In recent years, such a photographing apparatus as a camera has been popularized in progress, and a photographing opportunity has also been increased. Accordingly, there has been increased in the demands for making a silver halide photographic light-sensitive material higher in sensitivity and image quality.
One of the dominant factors for making a silver halide photographic light-sensitive material higher in sensitivity and image quality is a silver halide grain. Such a silver halide grain as is aimed at making sensitivity and image quality higher have so far been developed in progress by the art.
However, as has generally been developed so far, there has been a tendency to lower a sensitivity as the grain size of the silver halide grain has been made smaller for improve the image quality, so that there has been a limitation to make both sensitivity and image quality higher.
For making sensitivity and image quality more higher, there have been some techniques for improving a ratio of sensitivity/grain size per one silver halide grain. Among the above-mentioned techniques, the techniques in which a tabular-shaped silver halide grain is used have been described in, for example, Japanese Patent Publication Open to Public Inspection (hereinafter referred to as JP OPI Publication) Nos. 58-111935/1983, 58-111936/1983, 58-111937/1983, 58-111927/1983 and 59-99433/1984. As compared such a tabular-shaped silver halide grain to a regular-crystallized silver halide grain having, for example, octahedron and hexahedron, the surface area of the former tabular-shaped silver halide grain becomes larger than that of the latter when both silver halide grains have each the same volume. Therefore, the former silver halide grain has such an advantage that a more higher sensitivity can be provided, because more sensitizing dyes can be adsorbed to the surface of the former.
JP OPI Publication No. 63-92942/1988 discloses a technique in which a core having a high silver iodide content is contained inside a tabular-shaped silver halide grain; JP OPI Publication No. 63-151618/1988 discloses a technique in which a hexahedral tabular-shaped silver halide grain is used; and JP OPI Publication No. 63-163451/1988 discloses a technique in which a tabular-shaped silver halide grain is so used as to have a ratio of a grain thickness to the farthest distance from and to the twinned crystal surfaces of not higher than 5. These techniques show each the effects on sensitivity and graininess.
As described above, in addition to the technique in which a high sensitivity can be made higher by improving the structure and form of a grain, there is also another known technique in which the movements of photoelectron and positive hole are improved inside a silver halide grain by doping a metal ion in the silver halide grain, so that the photographic characteristics can be renovated.
As for the techniques in which a metal ion is so added as to achieve a high sensitization, JP OPI Publication Nos. 61-160739/1986 and 62-260137/1987 disclose each the techniques in which a polyvalent metal salt such as those of lead and cadmium is added; and JP OPI Publication No. 1-121844/1989 discloses a technique in which an iron compound is doped in a narrow band-gapped layer comprising a grain having a multilayered structure. Besides, each of JP OPI Publication Nos. 2-20852/1990, 2-20853/1990, 2-20854/1990, 2-222653/1990 and 2-224545/1990 discloses the technique in which a polyvalent metal and a novel ligand are used in combination.